The 1.36.0-wmf.28 version of MediaWiki is blocked[0]. The new version is deployed to testwikis, but can proceed no further until these issues are resolved:

* MediumSpecificBagOStuff.php Undefined offset errors: https://phabricator.wikimedia.org/T273006

* CacheTime.php Undefined index Version
https://phabricator.wikimedia.org/T273007
(should be resolved during the next roll forward attempt)

* Failed assertion in TableFixups handler
https://phabricator.wikimedia.org/T265720
(may be downgraded from unbreak-now).

Once these issues are resolved train can resume. If these issues are resolved on a Friday the train will resume Monday. Thank you for your help resolving these issues! -- Your humble train toiler

[0]. <https://phabricator.wikimedia.org/T271342>